The present invention relates to controlling gastrointestinal parasitic infections in animals, and more particularly to methods and compositions for controlling gastrointestinal nematodal infections in animals, especially ruminants.
In the southern USA, goat production for meat or milk is an attractive alternative enterprise for farmers because of comparatively low cost of breeding stock, high reproductive rate of goats, and their ability to thrive on native pastures or brushland that is unsuitable for cropping (Glimp et al, 1896, “Strategies for Expanding Goat Meat Product Processing, and Marketing in the Southeastern US”, Winrock International, Morrilton, Ark.). In addition, there is high ethnic demand for goat meat and milk products in the USA, particularly in large metropolitan areas, which is exceeding current production levels. Despite increasing demand for goat products, growth of the goat industry in the southern USA has been slow. The major hindrance to economic goat production in this region is infection with gastrointestinal nematodes (GIN), particularly Haemonchus contortus. The conventional method of GIN control by farmers in the Southeast is regular use of anthelmintics, sometimes monthly or more during the warm season. Overuse and/or misuse of anthelmintics has led to increased anthelmintic resistance in GIN of goats, sheep, and cattle in many parts of the world (Prichard, 1994. “Anthelmintic Resistance”, Vet. Parasitol, 54:259-268), and recent reports from Virginia (Zajac et al, 2000, “Multiple Anthelmintic Resistance in a Goat Herd”. Vet. Parasitol. 87:163-172) and Georgia (Mortensen et al, 2003. “Evaluation of Prevalence and Clinical Implications of Anthelmintic Resistance in Gastrointestinal Nematodes in Goats”. JAVMA 223:495-500) indicate that anthelmintic resistance in goats has become highly prevalent in the southern USA.
In traditional veterinary medicine, which is still practiced in many parts of the world, the use of plants with anthelmintic properties has been considered as an alternative to anthelmintic drugs. Grazing forages high in tannins or adding purified condensed tannins (CT) to the diet has been shown to reduce parasite eggs in sheep and goat feces in a number of studies (Niezen et al, 1998; “Production, Fecal Egg Counts and Worm Burdens of Ewe Lambs which Grazed Six Contrasting Forages”. Vet. Parasit. 80:15-27; Athanasiadou et al, 2000; “Consequences of Long-Term Feeding with Condensed Tannins on Sheep Parasitized with T. colubriformis”. Int. J. Parasitol. 30:1025-1033; Min et al, 2003. “Tannins for Suppression of Internal Parasites”. J. Anim. Sci. 81 (E. Suppl. 2). E102-E109; Paolini et al, 2003, “Effects of Condensed Tannins on Goats Experimentally Infected with Haemonchus contortus”, Vet. Parasit. 113:253-261.). Paolini et al, 2003, “Effects of Sainfoin Hay on Gastrointestinal Nematode Infections in Goats”, Vet. Record 152:600-601 reported lower egg count in feces of goats fed sainfoin (Onobrychi viciifolia Scop.) hay compared with grass hay, but the anthelmintic effects of feeding hay from CT-containing forages is not well documented.